Welding electrode



Aug. 9, 1932. v Q A, CADWELL 1,871,257

' WELDING ELECTRODE Filed Oct. 19, 1925 METALLIC PENCIL.

VA RIV S/Y SURI'A SILICON cane/v. x7 CLAY COATING SlL/cArE5 G UM IINVENTOR. I z I Char/a6 A. C'aawe/Z A TTOR Patented Aug. 9, 1932 UNITEDSTATES PATENT OFFICE CHARLES A. CAD'WELL, OF CLEVELAND HEIGHTS, OHIO,ASSIGNOR TO THE ELECTRIC RAILWAY IMPROVEMENT COMPANY, OF CLEVELAND,OHIO, A CORPORATION OF OHIO WELDING ELECTRODE Application filed October19, 1925. serial No. 63,299.

The present improvements, relating, as indicated, to metallicelectrodes, have more particular regard to coated metallic pencils (rodsor wires) of the type used in arc weld- It has been the practice forsome time in metal working by electricity to employ what are known ascoated metallic pencils in order either to introduce alloying andreducing ingredients into the weld or to secure certain other desirableresults in the manipulation of the pencil. For example, a bare metallicpencil or electrode if not carefully handled is apt to stick to the workwith consequent damage and delay. Accordingly, the coatings heretoforeused have been composed of materials that when highly heated form a slagadapted to protect the metal of the weld from oxidation and from toorapid chilling, and such materials have also been selected with a viewto their insulating character, which is of value to the operator incertain cases. Asbestos and chalk are examples of the materials justreferred to. The purpose in employing an alloying or reducing agent inthe coating is of course obvious and this has been introduced, forexample, in the form of a fine wire interwoven with the material of thecoating or of a metallic powder added to such material.

The object of the present improved coating is to overcome difficultiesof a different character, for the meeting of which none of the coatingsheretofore employed or proposed, so far as I am aware, is suited. Tothis end I employ a com osition differing radically from any heretoforeemployed in coatings of the type in question. For example, instead of aninsulating material, I employ one that is a fairly good conductor evenwhen cold. Furthermore, the coating instead of melting at a temperaturelower than that of the metal of the electrode, melts at a highertemperature and so tends to assume the form of an annular extension orsleeve that projects beyond the point of the electrode so as to retardthe deposition of metal and generate a higher temperature to acorresponding greater penetration or depth of weld. Furthermore, thecoating material inknown cold shot weakness.

cludes an ingredient which under the heat of the arc is decomposed intoa reducing element or elements which react with the metal of the weld toovercome oxidation and to improve the quality of such metal.

To the accomplishment of the foregoing and related ends, the invention,then, consists of the ingredients and resultant coated producthereinafter fully set forth and particularly pointed out in the claims,the an The invention will be first describedwith particular reference tocoated copper are weld pencils such as are employed, for ex ample, 1ncertain known methods for attaching copper bonds to steel rails. In suchcase, a bare metallic copper electrode deposits metal in large globuleswhich fall intermittently from the point of the electrode and whichamalgamate with each other only in case the temperature of the work ishigh enough to prevent a chill of the first drop before the next shallhave fallen. Inasmuch as copper is a metal of relatively low meltingpoint, a chilled or cold shot condition is always found at the bottom ofa copper are weld made with bare pencil. Particularly is this true inthe application of this method of welding to rail bonding, where thefirst drops from the cou er electrode may fall on the cold copper of theconductor.

Even if a mold or dam be used in an effort to puddle the mass of themetal deposited into a molten lake, the critical part of the weld, thatis, the contact, where the first metal from the electrode falls, willshow the well If the bare copper electrode is used to deposit metal instrings or layers, as for instance on top of the lower flange of a rail,the mass deposited will be found to resemble a conglomerate of nodulespoorly bonded together.

The difficulties attendin the use of a bare copper electrode for railonding, resulting from cold shot effect, are greatly increased by thecondition of the surface of the rail to be bonded. Any reducing agentintroduced as an alloy into the copper metal of the electrode, capableof reacting with the oxide found on the surface of the average rail,requires more heat for a good reaction than can ossibly be obtained fromthe cold shot metal dropped intermittently from a bare copper electrode,although it must be said that the chilling effect of a steel body ismuch less than one of copper and that on a comparatively clean rail,copper are metal from a bare electrode makes better contact with thesteel than it does with the copper of the bond conductor. The greatestdifliculty from poor rail contact in using a bare copper electroderesults from an adverse polarity. The common practice on electricrailways of using trolley current direct through a rheostat, withouttransformation, for bonding, dictates that a positive electrode be usedon track rail and a negative electrode on third rail. The greatestdifference exists in the action of a bare copper electrode in the twocases. A drop of metal falling from the end of a ositive electrode dropsdownwards, while rom the end of a bare negative pencil, working on thirdrail, the drops of metal are propelled with force by a. flickering,fitful arc flame that sends the successive drops in unexpecteddirections.

. As previously indicated, I have discovered that if there be applied acoating to such a copper welding pencil, which is not only an agent forthe reduction of any oxides of iron or copper that might occur at or inthe weld, but which under the action of the are becomes a plastic tubeencasing the copper at the pointof the electrode and draws somewhat overthe point like a glass tube softened by heat for sealing, not only isthe actual welding operation facilitated, but a much more homogeneousjuncture is obtained between the parts being welded together, e. g. bondand rail. By employing for this coating a material that not only becomesthus plastic upon heating, but is also a good conductor with a meltingpoint considerably higher than copper, the deposition of molten copperis greatly retarded with a corresponding increase in the amount of heatintroduced into the weld. In fact, the action of this coated pencil ismore that of an ideal selffeeding, non-metallic are, under which themolten copper is deposited more as a continuous spray of highlysuperheated metal than as a succession of the large drops from a baremetallic electrode. The absence of large drops and a spraying action asfrom an atomizer results from the constricted, plastic and overshotenvelope of the electrode end which exercises a capillary attraction forthe molten metal before it can collect in large drops, and also from thevolatilization of certain elements in the coating which help to break upmetallic globules.

The thickness and composition of the coat ing may be varied to secureany degree of heat, with accompanying slower rate of deposition desired,the limit being a coating so refractory that after the first few dropsof copper have fallen, the end of the copper rod will have retreated toa distance above the end of the electrode, which end, from the materialof the coating alone, becomes a very stable non-metallic electrode, withthe result that no more, or very little, copper will fall and only aheating are will remain.

I have found that carborundum or silicon carbide, SiC, constitutes, whensubjected to the action of the arc flame, a satisfactory material forthe reduction of the oxides that occur in welding and at the same timeprevents oxidation from the air and insures a sound set in the copperdeposited. This compound or material also introduces elements fordeoxidation which, if they occur in excess of oxidation needs, willalloy with both the copper and steel of the weld, while such material isalso a conductor of the current of the are and thus when the coatingprojects as an overshot envelope at the end of the electrode, it willcarry the current where the heat intensity is greatest and thus retardthe flow of metal and consequently introduce more heat into the weld.Finally,it is refractory under heat with a melting point considerablyabove that of the ordinary metals.

In order to impart to the coating composition a plastic condition whenit approaches the melting point, so that it will not fall off in crumbs,it is desirable to admix with such silicon carbide a binding materialsuch as high silica clay, in which the binding quality is developed bythe addition of water.

It is also desirable to include in the composition a certain amount ofvolatile matter to assist in breaking up large globules of molten metalas well as provide a fluid slag for floating off refractory crumbs, andfor this purpose the fusible silicates comprised in common bottle glass,for example, may be added to the clay binder.

Finally, in order that the composition may be quickly and cheaplyapplied to the metallic pencil and be secured against dislodgment fromhandling, a suitable water soluble gum is added, a relatively smallquantity of this in combination with the clay binder being sufficientfor the purpose. The following is typical of a satisfactory compositionincluding the ingredients named above, viz

Per cent Silicon carbide 68.5 Clay 10.5 F usible silicates 16.5 Gum 4.5

The foregoing percentages are based on the weight of the materials whendry, the materials being mixed in this condition and then made into athin paste by'the addition of water and applied to the rod or pencilwith a brush. After drying a coat of varnish may be added to toughen theskin of the coating.

7 In the process of welding the varnish and I form of the are as itattaches to thepoint of the electrode in the onecase or the other. Thus,as shown in Fig. 2, where the electrode is on the positive side, theadjacent portion of the arc is more or less confined to the exposed endof the metallic pencil, while, as shown in Fig. 3, where the electrodeis on the negative side, the arc assumes a more spreading form andattaches to the projecting coating envelope as well as to the end of themetallic pencil; 'however, such envelope tends to close more or lessacross such end. In both cases the metal will lie back of the end anappreciable distance and will always present a clean appearance when thearc is discontinued, showing that there is no tendency for the metal tooxidize before it is deposited.

In case the deposition of the metal is unduly retarded, the projectingenvelope or the outer portion thereof may be readily broken ofl bylightly striking the same against the parts being welded; while, on theother hand, if a coating of sui'ficient thickness is employed, bypropermanipulation the arc "may be struck entirely from. such projectingenvelope portion and used as a cutting arc.

While the melting point of iron or steel is considerably higher thanthat of copper, the

temperature at which the-envelope will melt is still higher andsubstantially the same operative results. are obtained where my improvedcoating is used on such iron or steel my invention may be employedinstead of the one explained, change being made as regards the materialsemployed, provided the ingredients or elements stated by any of thefollowing claims or the equivalent of such stated in redients orelements be employed.

I there ore particularly point out and distinctly claim as my invent1on:

1. An electrode for electric arc weldin which comprises a coppercontaining metal .lic rod and an envelope thereon containing siliconcarbide in substantial proportion.

2. An electrode for electric arc weldin which comprises a coppercontaining metal lic rod and an envelope thereon containing about 68 percent of silicon carbide.

Signed by me, this 13th day of October,

' CHARLES A. GADWELL.

pencil as with a copper pencil. Obviously it may be employed with equaladvantage as a coating for pencils composed of other metals or alloyshaving the same relationship in the matter of temperature of fusion.

Other modes of applying the principle of

